1. Field of the Invention
The present invention relates to a method for detecting a nucleic acid contained in a target organism in a sample, a probe design method, and a probe design system therefore. More particularly, the present invention relates to a method for detecting DNA, which may originate from microorganisms etc. and exist in a sample, such as blood, based on a novel designing technology of probes.
2. Description of the Related Art
It is desired to treat a patient suspected of combined infection more quickly and appropriately.
To that end it is necessary to identify accurately microorganisms infecting the subject patient. A method for identifying microorganisms in a sample by hybridizing a DNA extracted from the sample, such as blood taken from a patient, with a probe specific to a possibly infected microorganism, and detecting a hybrid product, is under study as one of the methods. The accuracy of the detection of microorganisms in a sample depends on the designed specificities of probes for the respective microorganisms to the DNA corresponding to such respective microorganisms. For example using a probe hybridizing to both Staphylococcus aureus and Pseudomonas aeruginosa, it is not possible to identify accurately microorganisms. In other words, it is important to design a probe capable of avoiding cross-hybridization for an accurate identification of microorganisms. The present inventors have applied a patent disclosing a probe including nucleotide sequences discriminating separately a plurality of infectious pathogenic microorganisms (Japanese Patent Application Laid-Open No. 2004-313181). However, if in the future, a need occurs to detect more diversified microorganisms in a sample, a plain extension of the technology requires discovering a unique sequence specific to each of all such diversified microorganisms. This requires increased number of calculations demanding a long time for designing probes.
Further, with increase of the numbers of the target microorganisms, it is expected that such unique nucleotide sequence cannot be selected any more with respect to a certain microorganism, as is completely free from any cross-hybridization with all target microorganisms other than said microorganism.